1. Field of the Invention
This invention pertains generally to circuit interrupters and, more particularly, to arc fault and/or ground fault circuit interrupters including test circuitry.
2. Background Information
The National Electrical Manufacturers Association (NEMA) is looking for a clear indication of when a ground fault circuit interrupter (GFCI) reaches the end of its life and is not capable of providing ground fault protection. An opportunity exists when a user employs a test button on a GFCI. Since testing is a relatively infrequent event, an uneducated user may not remember what to expect and, if nothing happens (e.g., the GFCI fails to trip in response to the test button being depressed), the user may accept that result, in error, as being acceptable. Loss of ground fault protection may result in equipment damage, serious bodily injury or death in the event of an unprotected ground fault.
It is known to provide a GFCI receptacle with a visual indicator, such as a light-emitting diode (LED), to indicate that the circuit to which the receptacle is connected is operating normally. See, for example, U.S. Pat. Nos. 4,412,193; 4,568,997; and 5,202,662. The lit LED provides a visual indication that the circuit in which the GFCI is installed is operating normally without any ground fault. Upon occurrence of a ground fault, the LED is cut off and the light is extinguished. An extinguished LED provides a visual indication that a fault exists in the circuit. The LED can also be used to test for reverse installation of the GFCI. Should the load terminals be inadvertently connected to the power line and the line leads mistaken for the load leads, the LED will remain lit at all times, even after a test button is actuated, since power will be continuously applied to the terminals across the LED circuit.
U.S. Pat. No. 4,351,013 discloses a circuit interrupter in which a trip unit initiates a tripping operation responsive to a ground fault condition. When tripping occurs, the ground fault condition is indicated by energization of an LED.
U.S. Patent Application Publication No. 2004/0056664 discloses turning a transistor on to activate a fault lamp, thereby indicating a failure of a GFCI circuit.
U.S. Pat. No. 6,697,238 discloses a GFCI including a green LED and a red LED purports to provide a visual indication of the status of the GFCI. When a test switch is pressed and closes primary test switch contacts and an imbalance is created, relays open and cause the green LED to be extinguished. Since the relays are open, subsequent closing of secondary test switch contacts by the test switch has no affect on the GFCI. In contrast, if the closing of primary test switch contacts fail to trip the GFCI, then the secondary test switch contacts cause a short circuit blowing a fuse and extinguishing the green LED. However, a red LED is illuminated to indicate that the GFCI is operating as an unprotected receptacle and not as a GFCI.
There is room for improvement in circuit interrupters including ground fault test circuitry.
There is also room for improvement in circuit interrupters including arc fault test circuitry.